This invention is generally relative to short-range wireless ultra wideband (UWB) communications for indoor and outdoor operations.
On Apr. 22, 2002, U.S. Federal Communications Commission (FCC) released the revision of Part 15 of the Commission's rules regarding UWB transmission systems to permit the marketing and operation of certain types of new products incorporating UWB technology. With appropriate technology, UWB devices can operate using spectrum occupied by existing radio service without causing interference, thereby permitting scarce spectrum resources to be used more efficiently. It has been believed that UWB technology offers significant benefits for Government, public safety, businesses, and consumers under an unlicensed basis of operation spectrum.
The UWB devices can be classified into three types based on the operating restrictions: (1) imaging system including ground penetrating radars and wall, through-wall, surveillance, and medical imaging device, (2) vehicular radar systems, and (3) communications and measurement systems. In general, FCC is adapting unwanted emission limits for the UWB devices that are significantly more stringent than those imposed on other Part 15 devices. In other words, FCC limits outdoor use of the UWB devices to imaging systems, vehicular radar systems, and hand held devices. Limiting the frequency bands, which is based on the −10 dB bandwidth of the UWB emission, within certain UWB products will be permitted to operate. For communications and measurement systems, FCC provides a wide variety of the UWB devices, such as high-speed home and business networking devices as well as storage tank measurement devices under Part 15 of the Commission's rules subject to certain frequency and power limitations. The UWB device must operate in the frequency band from 3.1 GHz to 10.6 GHz. The UWB devices should also satisfy the Part 15.209 limit, which sets emission limits for indoor and outdoor UWB system, for the frequency band below 960 MHz and conform the FCC's emission masks for the frequency band above 960 MHz.
For indoor UWB communication operation, Table 1 lists the FCC restrictions of the emission masks (dBm) along with the frequencies (GHz).
TABLE 1Frequency (MHz)EIRP (dBm) 0–960−41.3 960–1610−75.31610–1990−53.31990–3100−51.3 3100–10600−41.3Above 10600−51.3
Outdoor handheld UWB communication systems are intended to operate in a peer-to-peer mode without restrictions on a location. However, the outdoor handheld UWB communication systems must operate in the frequency band from 3.1 GHz to 10.6 GHz, with an extremely conservative out of band emission masks to address interference with other communication devices. The outdoor handheld UWB communication systems are permitted to emit at or below the Part 15.209 limit in the frequency band below 960 MHz. The emissions above 960 MHz must conform to the following emission masks as shown in Table 2:
TABLE 2Frequency (MHz)EIRP (dBm) 0–960−41.3 960–1610−75.31610–1900−63.31900–3100−61.3 3100–10600−41.3Above 10600−61.3
FCC proposed to define an UWB device as any device where the fractional bandwidth is greater than 0.25 based on the formula as follows:
                              FB          =                      2            ⁢                          (                                                                    f                    H                                    -                                      f                    L                                                                                        f                    H                                    +                                      f                    L                                                              )                                      ,                            (        1        )            where fH is the upper frequency of the −10 dB emission point and fL is the lower frequency of the −10 dB emission point. The center frequency of UWB transmission is defined as the average of the upper and lower −10 dB points as follows:
                              F          C                =                                                            f                H                            +                              f                L                                      2                    .                                    (        2        )            
In addition, a minimum frequency bandwidth of 500 MHz must be used for indoor and outdoor UWB communication devices regardless of the center frequency.
The UWB communication devices must be designed to ensure that the indoor operations can only occur in an indoor environment according to the indoor emission masks in Table 1. On the other hand, they must be designed as hand-held UWB devices that may be employed for such activities as peer-to-peer operations according to the outdoor emission masks in Table 2. Such UWB communication devices can be used for wireless communications, particularly for short-range high-speed data transmissions suitable for broadband access to networks.
Since the indoor and outdoor UWB communication devices may have similar structures and operation functions, designing a dual-mode UWB communication device with the ability of using in the indoor and outdoor operation is crucial. This leads to save the cost for a dual-mode indoor and outdoor UWB communication transceiver. However, the dual-mode indoor and outdoor UWB communication transceiver needs to have different transmission and receiver filters, which are key elements to make such the UWB communication transceiver successfully. This is because the dual-mode indoor and outdoor UWB communication transceiver has to meet the different masks of the FCC emission limitations for indoor and outdoor operations.
Thus, there is a continuing need for the UWB communication transceiver with employing a dual-mode architecture of digital transmission-shaping filters and receiver filters for the indoor and outdoor operations.